﻿using System;
using System.Collections.Generic;
using System.IO.Ports;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace ljh.ModbusRTULib
{
    public class ModbusRTU
    {
        //串口对象
        private SerialPort serialPort = null;

        /// <summary>
        /// 无参构造方法
        /// </summary>
        public ModbusRTU() { }

        /// <summary>
        /// 有参数构造方法
        /// </summary>
        /// <param name="delay">接收报文延时（整数）</param>
        public ModbusRTU(int delay)
        {
            this.ReceiveDelay = delay;
        }

        //接收报文延时
        //public int ReceiveDelay { get; set; }  
        //这样写，对延时时间没有限制，很容易出问题

        /// <summary>
        /// 接收报文延时
        /// </summary>
        private int _receiveDelay = 100;
        public int ReceiveDelay
        {
            get
            { 
                return _receiveDelay; 
            }
            set
            {
                if (value < 10 || value > 2000) //可以自己定义范围
                {
                    _receiveDelay = 100;
                }
                else _receiveDelay = value;
            }
        }

        /// <summary>
        /// 打开串口
        /// </summary>
        /// <param name="portName">串口号</param>
        /// <param name="baudRate">波特率</param>
        /// <param name="parity">校验位</param>
        /// <param name="dataBits">数据位</param>
        /// <param name="stopBits">停止位</param>
        public void Connect(string portName, 
                            int baudRate = 9600,
                            Parity parity = Parity.None,
                            int dataBits = 8, 
                            StopBits stopBits = StopBits.One)
        {
            //实例化串口对象
            serialPort = new SerialPort(portName, baudRate, parity, dataBits,
                stopBits);
            try
            {
                serialPort.Open();
            }
            catch (Exception ex)
            {
                throw new Exception("串口打开失败！原因：" + ex.Message);
            }
        }
        /// <summary>
        /// 关闭串口
        /// </summary>
        public void DisConnect()
        {
            if (serialPort != null && serialPort.IsOpen)
            {
                serialPort.Close();
            }
        }
        /// <summary>
        /// 读取保持寄存器，功能码03H
        /// </summary>
        /// <param name="slaveID">从站ID</param>
        /// <param name="startAddress">起始寄存器地址（10进制）</param>
        /// <param name="count">寄存器数量</param>
        /// <returns>只有数据的字节数组</returns>
        public byte[] ReadHoldingRegister(byte slaveID, int startAddress, int count)
        {
            //第一步：封装【请求】报文
            //从站地址+功能码+起始地址高位+起始地址低位+寄存器数量高位+寄存器数量低位+CRM校验
            byte[] sendBytes = new byte[8];
            sendBytes[0] = slaveID;//从站地址
            sendBytes[1] = 0x03;//功能码
            //封装寄存器起始地址
            sendBytes[2] = (byte)(startAddress / 256);//将int类型的地址，获取转换后的字节高位
            sendBytes[3] = (byte)(startAddress % 256);//将int类型的地址，获取转换后的字节低位
            //封装寄存器数量
            sendBytes[4] = (byte)(count / 256);
            sendBytes[5] = (byte)(count % 256);
            byte[] crc = CRC16(sendBytes, 6);//封装CRC校验校验前面6位
            sendBytes[6] = crc[0];
            sendBytes[7] = crc[1];

            //第二步：发送【请求】报文
            byte[] receiveBytes = null;
            try
            {
                serialPort.Write(sendBytes, 0, sendBytes.Length);//发送报文，等待返回
                Thread.Sleep(ReceiveDelay);//接收缓冲，否则太快

                //第三步：接收【应答】报文
                receiveBytes = new byte[serialPort.BytesToRead];
                //从缓冲区接收全部报文到指定数组
                serialPort.Read(receiveBytes, 0, receiveBytes.Length);
            }
            catch (Exception ex)
            {
                throw new Exception("发送或接收报文出现问题：" + ex.Message);
            }
            //第四步：解析【应答】报文
            int byteLength = 2 * count;//返回的数据字节计数=4个字节 (寄存器数量*2）
            //报文长度必须合理（5=> 地址 + 功能码 + 字节计数 + 2个CRC校验
            if (receiveBytes.Length == 5 + byteLength)
            {
                //进一步校验
                if (CheckCRC(receiveBytes) && receiveBytes[1] == 0x03
                    && receiveBytes[2] == byteLength)
                {
                    byte[] returnDataArray = new byte[byteLength];//用于返回的数据数组

                    //返回截取后只包括数据的数组（从索引3开始（去掉地址、功能码、字节计数），
                    //目的数组，从0开始，复制数据长度）
                    Array.Copy(receiveBytes, 3, returnDataArray, 0, byteLength);
                    return returnDataArray;//返回的数组，只包括数据
                }
                else return null;
            }
            else return null;
        }

        #region  CRC校验【查表法，速度很快】

        private static readonly byte[] aucCRCHi = {
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
             0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
             0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
             0x00, 0xC1, 0x81, 0x40
         };
        private static readonly byte[] aucCRCLo = {
             0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7,
             0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E,
             0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09, 0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9,
             0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC,
             0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
             0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32,
             0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D,
             0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A, 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38,
             0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF,
             0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
             0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1,
             0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4,
             0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB,
             0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA,
             0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
             0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0,
             0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97,
             0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C, 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E,
             0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89,
             0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
             0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83,
             0x41, 0x81, 0x80, 0x40
         };
        private byte[] CRC16(byte[] pucFrame, int usLen)
        {
            int i = 0;
            byte[] res = new byte[2] { 0xFF, 0xFF };
            ushort iIndex;
            while (usLen-- > 0)
            {
                iIndex = (ushort)(res[0] ^ pucFrame[i++]);
                res[0] = (byte)(res[1] ^ aucCRCHi[iIndex]);
                res[1] = aucCRCLo[iIndex];
            }
            return res;
        }

        private bool CheckCRC(byte[] value)
        {
            if (value == null) return false;

            if (value.Length <= 2) return false;

            int length = value.Length;
            byte[] buf = new byte[length - 2];
            Array.Copy(value, 0, buf, 0, buf.Length);

            byte[] CRCbuf = CRC16(buf, buf.Length);
            if (CRCbuf[0] == value[length - 2] && CRCbuf[1] == value[length - 1])
            {
                return true;
            }
            return false;
        }
        #endregion
    }
}
